The Big Ratchet: How Humanity Thrives in the Face of Natural Crisis by Ruth DeFries Read Free Book Online Page B

environment set the pace for evolution.
    But Darwin struggled to explain how human culture—ideas that boost our species’ success as they pass from one generation to the next and from one place to another—fit within his theory of natural selection. In his famous 1874 treatise The Descent of Man , he hinted at the notion that the powerful force of natural selection weakens as human culture becomes more complex. “With highly civilized nations, continued progress depends in a subordinate degree on natural selection,” he wrote. “The more efficient causes of progress seem to consist of a good education during youth while the brain is impressible, and of a high standard of excellence, inculcated by the ablest and best men, embodied in the laws, customs, and traditions of the nation, andenforced by public opinion.”
    Three-quarters of a century later, the Russian biologist Theodosius Dobzhansky and British American anthropologist Ashley Montagu picked up the question of how human culture evolves, concluding that “instead of having his responses genetically fixed as in other animal species, man is a species that invents its own responses, and it is out of this unique ability to invent, to improvise his responses thathis cultures are born.” Despite the interest of Darwin, Dobzhansky, and Montagu in the subject, today only a small number of anthropologists, biologists, and psychologists devote their careers to intriguing and thorny questions about the forces that shape the evolution of human culture. Among them are Peter Richerson and Robert Boyd, who rely on modern mathematical models and laboratory experiments to piece together the puzzle of how genes and culture intertwine and coevolve. Their goal is to explain why humans, rather than our chimp or bonobo cousins, have the extraordinary ingenuity to dominate the world.
    Culture enabled the Inuit to adapt to the harsh Arctic environment through customs, traditions, and socially accepted norms. Cultureexplains the different fates of Franklin’s crew and the Inuit in those long, dark winters. How culture evolved and shaped our species’ destiny might be one of the most fascinating unresolved puzzles of human history. As Richerson and Boyd put it, “culture would never have evolved unless it could dothings that genes can’t!”
    From Genes to Ingenuity
    Communication. Sharing information. Transmitting knowledge. These tools constitute the lifeblood of all cultures and the foundation for all life. When ancient forms of life acquired the machinery to store DNA and pass their genes to their offspring, they secured a means to transmit information to the next generation about how to survive in the environment. Through inheritance of genes, parents could “tell” their children what traits they had used to survive. Parents could communicate their success.
    All life, including humans and the other great apes, employ early life’s great invention, transmitting information from one generation to the next through genetic inheritance. The cost of passing on genes is minimal to the parents, and the savings to offspring are large. Offspring need not invest time or energy to learn everything about their environment. The information is hard-wired. So long as the environment doesn’t change so rapidly that the information becomes invalid, the hard-wired communication strategy of genetic inheritance beats out all others. Many species whose life-spans are short compared with the time scale of changes in their environment rely exclusively on this strategy, from those as simple as viruses to those as complicated as flies.
    But genetic inheritance is not foolproof. Unusually heavy rains hit the Galapagos Islands in the early 1980s. The rains produced abundant seeds for the finches, but favored the plants that produced small, soft seeds over those that produced large, hard ones. Finch species thatfed on large seeds were at a disadvantage, and their numbers dwindled. Those individuals